1. Field of the Invention
The present invention relates to a specific novel azo dye compound and a coloring composition containing the azo dye compound, as well as to a ink sheet for thermal transfer recording, a thermal transfer recording method, a color toner, an ink for inkjet and a color filter.
2. Description of the Related Art
Recently, the mainstream of an image-recording material is a material especially for forming color images; and concretely, a recording material for inkjet system, a recording material for thermal transfer system, a recording material for electrophotographic system, a silver halide photographic material for transfer system, a printing ink and a recording pen are much utilized. In a picture-taking element such as CCD in photographic instruments and in LCD or PDP in displays, used is a color filter for recording and reproducing color images.
In a color image-recording material and a color filter, used is a coloring agent of three primary colors (dyes, pigments) for reproducing and recording full-color images according to an additive color-mixing process or a subtractive color-mixing process. At present, however, no one knows a coloring agent that has an absorption characteristic capable of realizing a preferred color reproduction range and that is fast and durable under various working conditions, and improving it is greatly desired.
Thermal transfer recording includes a method of heating a thermal transfer material that has a hot-melt ink layer formed on a support (base film), with a thermal head to thereby melt the ink for recording on an image-receiving material; and a method of heating a thermal transfer material that has a thermal transfer dye-containing dye donor layer on a support, with a thermal head to thereby thermally diffuse and transfer the dye onto an image-receiving material. In the latter thermal transfer method, the amount of the dye to be transferred may be changed by changing the energy to be applied to the thermal head, and therefore the method facilitates gradation recording and is especially advantageous for full-color recording of high-quality images. However, the thermal transfer dye to be used in this method has many limitations, and there are known only an extremely few dyes satisfying all the necessary properties.
The necessary properties are, for example, the dye has a spectral characteristic favorable for color reproduction, it is easily transferable, it is fast to light and heat, it is fast to various chemicals, it is easy to produce, and it is easily processable to produce a thermal transfer recording material. However, conventional specific dyes that have been proposed to have a spectral characteristic favorable for color reproduction and to be fast to light and heat (for example, JP-A-1-225592, 63-189289) are not on a satisfactory level, and further improving them is greatly desired.
In electrophotographic color copiers and color laser printers, in general, widely used is a toner that comprises a coloring agent dispersed in resin particles. The necessary properties of color toner are an absorption characteristic capable of realizing a preferred color reproduction range, especially high transmittance (transparency) necessary for overhead projectors (hereinafter referred to as OHP), and various fastness under working conditions. Toners are proposed, comprising a coloring agent of pigment dispersed in particles (for example, JP-A-62-157051, JP-A-62-255956, JP-A-6-118715). These toners have excellent lightfastness, but easily aggregate as they are insoluble, therefore having problems in point of the transparency reduction and the transmitted color change. On the other hand, also proposed are toners comprising a coloring agent of a specific dye (for example, JP-A-3-276161, JP-A-2-207274, JP-A-2-207273). Contrary to the above, these toners have high transparency and have no color change, but have a problem in point of the lightfastness thereof.
An inkjet recording method has been greatly popularized these day and is being further developed, since its material cost is low, it enables high-speed recording, it makes few recording noises, and it facilitates color recording.
The inkjet recording method includes a continuous system where ink droplets are continuously jetted, and an on-demand system where ink droplets are jetted in accordance with an image information signal; and their jetting systems include a system where ink droplets are jetted out under pressure given thereto by a piezo element, a system where an ink is bubbled by heat and jetted out as droplets, an ultrasonic system, and a system of sucking in and jetting out ink droplets by electrostatic force. The ink for inkjet recording includes a water-base ink, an oil-base ink and a solid (hot-melt) ink.
The necessary properties of the coloring agent for use in the ink for such inkjet recording are that its solubility or dispersibility in solvent is good, it enables high-density recording, its color is good, it is fast to light, heat and active gases in the environment (oxidizing gases such as NOx, SOx, ozone), it is fast to water and chemicals, it well fixes in an image-receiving material with no bleeding, its storability in ink is good, it is not toxic, its purity is high, and it is inexpensive and is easily available. However, it is extremely difficult to obtain a coloring agent that satisfies these requirement on a high level. In particular, it is strongly desired that the coloring agent exhibits a good yellow color, its solubility is high, and it is fast to light, moisture and heat, especially highly fast to light.
Since a color filter is required to have high transparency, a coloring method of dyeing it with a dye has heretofore been employed. For example, a colorable photoresist is patternwise exposed to light and developed to form a pattern, and then this is dyed with a dye of a filter color. This method is repeated for all the filter colors, thereby producing a color filter. Apart form the coloring method, also employable is a method of using a positive resist for color filter production. The color filter produced according to these methods have high transmittance as comprising dyes, and its optical characteristic is good, but its lightfastness and heat resistance are limited. Accordingly, a coloring agent excellent in various resistance and having high transparency is desired. On the other hand, a method of using an organic pigment having excellent lightfastness and heat resistance in place of dye is widely known, but color filters with pigment could hardly have an optical characteristic like those with dye.
Common to them, dyes usable to the above-mentioned applications are desired to have the following properties. Specifically, they exhibit good color in color reproduction, they have an optimum spectral absorption, they have good fastness such as lightfastness, moisture resistance, chemical resistance, and their solubility is high.
For use in thermal transfer recording, proposed are an azo dye in which the coupling component is an aminopyrazole having a specific structure (JP-A-1-225592, JP-A-2-24191, JP-A-4-22714), and a dye in which the diazo component is imidazole (JP-A-62-55194, JP-A-63-5992). Also proposed is a dye in which the diazo component, imidazole has a substituent, carbonyl group introduced into the N-position thereof (JP-A-2002-60642, JP-A-2002-60643). However, these dyes are not always on a satisfactory level in point of the above-mentioned necessary characteristics, and are desired to be further investigated.